1. Field of the Invention
The embodiments of the subject matter disclosed herein generally relate to the storage of heat and release of pre-stored heat. More specifically, the embodiments relate to a vessel of a heat storage and release apparatus and energy production.
2. Description of the Prior Art
The demand for energy, particularly for electrical energy, varies considerably from time to time during a day, a week, a month or an year; however, energy production plants often produce energy on a relatively constant basis, thus, the production of energy is different from the demand. Examples of energy production plants whose production cannot be easily adapted to the demand are wind power plants and solar power plants.
There is known means to store energy during periods of low demand and to release it during periods of high demand.
A technology for doing so is based on compressed air and involves the storage of the compressed air in an excavated or natural cavern. Excess energy is used to operate a compressor which compresses air and sends it to the cavern during periods of low demand. During periods of high demand, the compressed air in the cavern is used to drive an expander for operating energy production equipment, for example, an electrical generation equipment.
During compression, air heats considerably (it may reach several hundred degrees Celsius); therefore, in the past, it has been conceived, according to an improved technology, to store the heat of the compressed air before storing the compressed air in the cavern at low temperature; when the compressed air in the cavern is required for producing energy, the stored heat is used to heat the compressed air coming from the cavern before providing it to the expander; for this purpose, heat storage and release apparatuses have been designed and used. In this way, the overall efficiency of the storage and release process is increased.
Known heat storage and release apparatuses take the form of hollow towers of reinforced concrete; they have a height of several meters (e.g. 50 m), a diameter of several meters (e.g. 20 m) and a wall thickness of few meters (e.g. 3 m).
Natural caverns, excavated caverns and such known heat storage and release apparatuses suffer from tightness problems. Additionally, their walls are subject to embrittlement due to the high pressure (e.g. 50 bar) and/or the high temperature (e.g. 500° C.) of the injected air and wet conditions that are often present worsen the situation. Finally, concrete walls are cumbersome and need to be cooled, for example, by forced water circulation next to or inside the walls when high-temperature air is injected into the apparatus.
Accordingly, it would be desirable to design and provide energy storage and release technology which overcomes the aforementioned drawbacks of the prior art.